Current concepts regarding autonomic cardiovascular control mechanisms have been formulated primarily from studies conducted in anesthetized experimental animals because it has not been possible to deliver precise, critically controlled autonomic stimuli to individual receptor areas in man. In this proposal, new, non-invasive techniques (including carotid baroreceptor stimulation with electronically conditioned neck suction) will be used to discover and characterize central nervous system autonomic mechanisms in healthy young volunteers; to elucidate pathophysiological and pharmacological mechanisms in young patients with borderline hypertension; and to study oscillator properties of the sinus node in normal subjects. These studies may provide insights into important autonomic mechanisms in normal man and may lead to a more complete understanding of the pathophysiology of essential hypertension.